The present invention relates to a press fastening and removable type fastening device, wherein fastening members are made of plastics, and engaging head portions of engaging projections provided on fastening members are engaged with each other.
Recently, a fastening device made of plastics and capable of press fastening and removing fastening members has been used in various portions.
FIGS. 6(a) and 6(b) are explanatory views for showing an example of use of the above described fastening device.
In FIGS. 6(a) and 6(b), P represents an instrument panel of an automobile; R represents a remote control device for an instrument built in the automobile; and F represents a fastening device. The fastening device F makes it possible to detachably attach the remote control device R to the instrument panel P.
Incidentally, the fastening device F is formed of two fastening members 1, and one of the fastening members 1 is fixed to the instrument panel P by, for example, a two-face adhesive tape, and the other of the fastening members 1 is fixed to the remote control device R by the two-face adhesive tape.
Therefore., for example, when a CD player is operated to listen to music, the remote control device R is held by hand to separate the fastening member 1 attached to the control device R from the fastening member 1 attached to the instrument panel, so that the remote control device R can be removed from the instrument panel P. Therefore, the CD player can be operated by using the remote control device R to listen to music.
When the remote control device R is not used, the fastening member 1 of the remote control device R is pressed against the fastening member 1 of the instrument panel P, so that the remote control device R is fixed to the instrument panel P, as shown in FIGS. 6(a) and 6(b).
In addition to this example, for example, in an automobile manufacturing department, the fastening device has been used as a member for joining interior parts, a joining member for preventing a head lining from hanging down, or a joining member for preventing a glass sheet from lifting.
FIG. 7 is a perspective view for showing an example of a fastening member for constituting a conventional fastening device as described above; FIGS. 8(a), 8(b) and 8(c) are an enlarged perspective view, an enlarged front view and an enlarged side view, of the engaging projection, respectively; FIG. 9 is a bottom view of a base for showing a positional relationship of legs; FIG. 10 is an explanatory view for showing spaces formed by the engaging projections; FIG. 11 is an explanatory view for showing a state of the respective engaging projections at the time of compression; and FIG. 12 is an explanatory view for showing a compression engagement condition of the fastening device.
In the drawings, reference numeral 1 denotes a fastening member integrally formed by injection molding of plastics by using a mold (two face dividing mold). The fastening member includes a flat base 2, and a plurality of engaging projections 4 provided on a main surface of the base 2 arranged in vertical and lateral rows.
Reference numeral 3 represents holes formed on the base 2, and the holes 3 are inevitably formed by the mold when the base 2 and the engaging projections 4 are integrally formed. The holes nave approximately the same shape and the size as those of engaging head portions 6 described later.
Each engaging projection 4 is formed of two legs 5A, 5B extending upwardly from the base 2, and the engaging head portion 6 situated on upper edges of the two legs 5A, 5B.
Incidentally, the engaging head portion 6 may have any desired shape, such as a circle or a polygon in its plane shape, and a dome or flat hemisphere shape in its side shape.
Spaces relative to the adjacent engaging projections 4 are explained. As shown in FIG. 10, when one engaging head portion 6 of the downwardly directed engaging projection 4 of one fastening member 1 is inserted into a cross shape space formed by four engaging head portions 6 of the engaging projections 4 arranged in two vertical rows and two lateral rows in the other fastening member, the engaging head portions 6 are arranged such that the downwardly directed engaging head portion 6 is engaged with the upwardly directed four engaging head portions 6. For example, assuming that a diameter of the engaging head portion 6 is D; a length between two centers of the adjacent engaging head portions 6 in lateral rows and vertical rows is S; and a length of a diagonal line between two centers of the engaging head portions 6 is T, the engaging head portions 6 are arranged to be D&lt;S&lt;2D, and D&lt;T&lt;2D.
Next, an explanation is made on the two fastening members engaging with and disengaging from each other.
To start with, the two fastening members 1, 1', which are exactly the same, are arranged such that the surfaces provided with the engaging projections 4, 4' face with each other. When one fastening member 1' is pressed against the other fastening member 1 so that the engaging head portions 6' of the fastening member 1' are inserted into the cross shape spaces formed by the engaging head portions 6 of the fastening member 1, since the engaging head portions 6' of the fastening member 1' are disposed to engage or interfere the engaging head portions 6 of the fastening member 1, the downwardly and upwardly directed engaging head portions 6, 6' are collided with each another, as shown in FIG. 11.
Under the condition, when the fastening member 1' is further pressed against the fastening member 1, the upper and lower engaging projections 4, 4' deform, and the engaging head portions 6' of the fastening member 1' pass through the spaces among the engaging head portions 6 of the fastening member 1, so that, as shown in FIG. 12, lower surfaces of the engaging head portions 6, 6' engage with each another to thereby form a compression fastening state.
When a force for releasing the engagement of the lower surfaces as described above is applied to the fastening member 1', the fastening member 1' is removed from the fastening member 1.
Incidentally, although the engaging head portion 6 is supported by two legs 5A, 5B as shown in FIG. 9, the legs 5, 5A and 5B may be arranged as in bottom views of the bases shown in FIGS. 13(a), 13(b) and 13(c).
In this case, when the engaging head portion 6 is supported by one leg 5 as shown in FIGS. 13(b) and 13(c), the thickness of the leg 5 may be made thicker than that of the legs 5A, 5B in view of strength.
In the fastening members 1, 1' for constituting the conventional fastening device F, the engaging head portions 6 of one fastening member 1 and the engaging head portions 6' of the other fastening member 1' are arranged to engage with each another. Therefore, when the fastening members 1, 1' are arranged to face with each other and are pushed with pressure in order to engage the engaging head portions 6, 6' as shown in FIGS. 10 and 11, since the engaging head portions 6, 6' do not have escaping spaces, they are forcibly pushed to each other.
Therefore, a large insertion force for engaging the engaging head portions 6, 6' together is required. As a result, there has been a disadvantage that the conventional fastening device F is not suitable for repeating use.
Accordingly, one object of the invention is to obviate the above disadvantage and to provide a fastening device, which is suitable for repeating use.
Another object of the invention is to provide a fastening device as stated above, wherein an insertion force for the engaging head portions can be greatly decreased without reducing a force for releasing the engagement of the engaging head portions.
A further object of the invention is to provide a fastening device as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.